Arnold & Son Ultrathin Tourbillon Skeleton known for its graceful curves, wide apertures, and slimness is now presented in a new case – with a diameter of 41.5 mm and a thickness of 8.4 mm. The new model is issued in two limited series of 28 watches apiece in red gold or platinum.
Inside, the A&S8320 calibre unveils its curves, apertures and details. At just 3.3 mm thick, it is one of the slimmest skeleton tourbillon calibres in existence. It is also a high-precision calibre because this one-minute flying tourbillon is assembled with a variable inertia balance for enhanced calibration stability.
The skeletonisation of the calibre reveals pronounced curves and numerous inflexion points that are highlighted by an original finish. On both the Ultrathin Tourbillon Skeleton Red Gold and Platinum, the bridges are treated with rose-gold PVD (4N) after being decorated with radiating Côtes de Genève stripes.
The flange around the calibre adopts this same finish, clearly revealing the Arnold & Son signature at 6H and enabling the off-centred white opal dial to be displayed in its purest form. The A&S8320 calibre was designed without an upper bridge to minimise its thickness.
The variable-inertia balance with inertia blocks ensures more precise calibration over time. The slender triangular carriage is supported by a double arrow, which is actually a counterpoise. The arrowhead on the staff of the escape wheel serves as a seconds pointer, as the carriage completes one rotation per minute.
The changes to the tourbillon carriage and regulating organ give the A&S8320 calibre a power reserve of 100 hours. This is a larger power reserve than for standard tourbillons, particularly slim ones.
